Offshore Helideck Ops
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The North Sea practice is to put the compasses to DG during before landing checks and then slave them after take off. For intensive shuttle flights, I would leave them on DG and maybe every 3rd of 4th take off re-slave them. IME most offshore installations will upset compasses by a good 30 or 40 degrees.
Avoid imitations
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Some years ago, I experienced a situation where we had to land on a rig to refuel, both outbound and inbound during a long range SAR. On the way out the compasses weren't affected. However, after refuelling a second time on the way back we departed with all three compasses reading differently. Until then, we had nothing in our SOPs to remind us to go to DG mode, but we did shortly after our return!
It did prove the benefit of carrying out gross error / compass checks though
It did prove the benefit of carrying out gross error / compass checks though
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I have been flying quite a lot from ships and oil rigs (mostly for SAR) in the Navy. We use the good old Lynx that also has a GM9 gyrocompass with both slaved and DG modes.
For any normal operation we leave the compass in slaved mode and make sure after take-off from a ship or rig that you (or the PNF) slaves the compass and checks it with the standby compass.
Only if the gyro compass has a problem, or if you are operating at for instance 75 deg north, we switch it to DG.
For any normal operation we leave the compass in slaved mode and make sure after take-off from a ship or rig that you (or the PNF) slaves the compass and checks it with the standby compass.
Only if the gyro compass has a problem, or if you are operating at for instance 75 deg north, we switch it to DG.
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Great answers! ... Looks like once the compass has been in the disturbance long enough and has been pulled out of whack, it takes a fair amount of time to recover. What are we talking about here? 5 minutes? ten minutes? longer?
Avnx EO
Avnx EO
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Avnx EO,
I do not know all the compass systems, but the GM9 in our Lynx helicopter has a socalled "fast slave" button.
Slaving the compass with this fast slave mode uses a speed of 30 deg/sec so it takes maximum 6 seconds...
Indeed if you have to wait for the slaving in the normal compass mode it would take much longer (i do not remember by heart, but i think it was about 1 deg/sec).
I do not know all the compass systems, but the GM9 in our Lynx helicopter has a socalled "fast slave" button.
Slaving the compass with this fast slave mode uses a speed of 30 deg/sec so it takes maximum 6 seconds...
Indeed if you have to wait for the slaving in the normal compass mode it would take much longer (i do not remember by heart, but i think it was about 1 deg/sec).
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How long it takes depends on how far it's off, and on the DG installation. In general, a couple of minutes is about as long as it takes, sometimes less. In a B412, you can manually swing the heading indicator and put it back right, in the S76 you just throw a switch and let it right itself. I've never timed it exactly, but 1 or 2 minutes is about as long as I recall.
How long it takes depends on how far it\'s off, and on the DG installation. In general, a couple of minutes is about as long as it takes, sometimes less. In a B412, you can manually swing the heading indicator and put it back right, in the S76 you just throw a switch and let it right itself. I\'ve never timed it exactly, but 1 or 2 minutes is about as long as I recall. But 2 minutes can seem like an eternity under some conditions.
How long it takes depends on how far it\'s off, and on the DG installation. In general, a couple of minutes is about as long as it takes, sometimes less. In a B412, you can manually swing the heading indicator and put it back right, in the S76 you just throw a switch and let it right itself. I\'ve never timed it exactly, but 1 or 2 minutes is about as long as I recall. But 2 minutes can seem like an eternity under some conditions.
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Turbulence criteria for offshore platform Ops
CAA Paper 2004/03 Helicopter Turbulence Criteria for Operations to Offshore Platforms
Safety Regulation Group
22 September 2004
SRG says:
The research reported in this paper was funded by the Safety Regulation Group of the UK CAA, and was performed by BMT Fluid Mechanics Limited, QinetiQ (Bedford) and Glasgow Caledonian University. The work was commissioned in response to a recommendation (10.2 (i)) that resulted from earlier research
into offshore helideck environmental issues, reported in CAA Paper 99004.
Turbulence around offshore platforms can represent a significant safety hazard and source of high cockpit workload. This was illustrated in the results of a questionnaire survey of offshore helicopter pilots, reported in CAA Paper 97009, where turbulence around platforms was ranked as the greatest of the fifteen factors contributing to workload and safety hazards that were considered.
Although the existing vertical wind speed criterion in CAP 437 in combination with a system of operational feedback (turbulence report forms) has served to contain the situation, the addition of a specific turbulence criterion which is calibrated to maximum safe pilot workload is viewed as a significant enhancement.
Work on validating the turbulence criterion using data from Bristow Helicopter’s helicopter operations monitoring programme (HOMP) is already underway. Once satisfactorily completed, the turbulence criterion will be added to CAP 437 and incorporated in the Offshore Helideck Design Guidelines document which the HSE commissioned with the support of the CAA, and is endorsed by the Offshore Industry Advisory Committee's Helicopter Liaison
Group (OIAC HLG).
A useful spin-off from the validation exercise will be the addition of an offshore helideck turbulence mapping capability to HOMP. This will enable helicopter operators with HOMP to better establish operating restrictions, and to monitor the turbulence environment around offshore platforms on a continuous basis with minimal effort. With this facility in place, any unannounced modifications to platform topsides adversely affecting the airflow over and around the helideck should be rapidly detected and appropriate changes to operating restrictions made.
Recommendations
Based on the conclusions of this report the following recommendations are made:
1 Use the criterion that the standard deviation of vertical velocity must not exceed 2.4 m/s as a working limiting turbulence criterion subject to further validation (subsection 9.1).
2 Reanalyse the predictors used to estimate HQR from pilot control activity using all the data available from the BRAE02 trial in order to derive coefficients of improved reliability for future general use (sub-section 4.6.8).
3 Seek validation of the entire modelling process and the limiting turbulence criterion against operational experience by means of:
a) Analysis of existing wind tunnel data using the new turbulence and existing vertical wind speed component criteria to predict the safe flight envelope for a number of offshore installations.
Compare the results with the Installation/Vessel Limitation
List (IVLL) for the installations concerned (sub-sections 8.6.1 and 9.1.2).
b) Implement the optimised HQR predictors (see recommendation 2 above) in the Helicopter Operations Monitoring Programme (HOMP) analysis, apply the analysis to the HOMP data archive and compare the resulting turbulence mapped around offshore installations with turbulent sectors as derived in a) above (subsections 8.6.2 and 9.1.2).
c) Use the analysis performed in b) above to identify specific severe turbulence events in the HOMP data archive, establish the turbulence levels likely to have been experienced from the associated wind conditions and wind tunnel data for the platforms concerned, and correlate this with the workload values obtained from the HOMP analysis (sub-sections 8.6.2 and 9.1.2).
4 Investigate the operational experience regarding the perceived increase in workload due to degraded visual conditions, and consider conducting further simulator trials to capture equivalent flight in turbulence data at night and in degraded meteorological conditions (sub-sections 4.6.7 and 9.1.2).
5 In the longer term, use data collected from the full-scale implementation of HOMP and optimised HQR predictors (see recommendation 2 above) to routinely map HQR around offshore installations, and make this information available to BHAB Helidecks to help improve and maintain the quality of the IVLL (sub-section 4.6.11).
6 Use data collected from the full-scale implementation of HOMP and optimised HQR predictors (see recommendation 2 above) to obtain evidence of any variation of turbulence induced pilot workload in different helicopter types. If it is apparent that significant differences are experienced across the offshore helicopter types in the fleet, consider extending the desktop simulation study to encompass selected types identified as particularly good or bad in this context (sub-section 5.2).
7 Consider re-assessing the 0.9 m/s vertical wind speed component criterion in the light of the new turbulence criterion (as proposed by [1]). However, note that this will require an improvement to the level of fidelity of the SyCoS model by implementing recent enhancements to produce more authentic control responses and consequently the ability to recognise and respect torque and power limits.
It's a big file (8.6mb). Dial-up users may wish to 'right-click' the link and select 'save target as...' to save the file.
Click: CAA Paper 2004/03
Safety Regulation Group
22 September 2004
SRG says:
The research reported in this paper was funded by the Safety Regulation Group of the UK CAA, and was performed by BMT Fluid Mechanics Limited, QinetiQ (Bedford) and Glasgow Caledonian University. The work was commissioned in response to a recommendation (10.2 (i)) that resulted from earlier research
into offshore helideck environmental issues, reported in CAA Paper 99004.
Turbulence around offshore platforms can represent a significant safety hazard and source of high cockpit workload. This was illustrated in the results of a questionnaire survey of offshore helicopter pilots, reported in CAA Paper 97009, where turbulence around platforms was ranked as the greatest of the fifteen factors contributing to workload and safety hazards that were considered.
Although the existing vertical wind speed criterion in CAP 437 in combination with a system of operational feedback (turbulence report forms) has served to contain the situation, the addition of a specific turbulence criterion which is calibrated to maximum safe pilot workload is viewed as a significant enhancement.
Work on validating the turbulence criterion using data from Bristow Helicopter’s helicopter operations monitoring programme (HOMP) is already underway. Once satisfactorily completed, the turbulence criterion will be added to CAP 437 and incorporated in the Offshore Helideck Design Guidelines document which the HSE commissioned with the support of the CAA, and is endorsed by the Offshore Industry Advisory Committee's Helicopter Liaison
Group (OIAC HLG).
A useful spin-off from the validation exercise will be the addition of an offshore helideck turbulence mapping capability to HOMP. This will enable helicopter operators with HOMP to better establish operating restrictions, and to monitor the turbulence environment around offshore platforms on a continuous basis with minimal effort. With this facility in place, any unannounced modifications to platform topsides adversely affecting the airflow over and around the helideck should be rapidly detected and appropriate changes to operating restrictions made.
Recommendations
Based on the conclusions of this report the following recommendations are made:
1 Use the criterion that the standard deviation of vertical velocity must not exceed 2.4 m/s as a working limiting turbulence criterion subject to further validation (subsection 9.1).
2 Reanalyse the predictors used to estimate HQR from pilot control activity using all the data available from the BRAE02 trial in order to derive coefficients of improved reliability for future general use (sub-section 4.6.8).
3 Seek validation of the entire modelling process and the limiting turbulence criterion against operational experience by means of:
a) Analysis of existing wind tunnel data using the new turbulence and existing vertical wind speed component criteria to predict the safe flight envelope for a number of offshore installations.
Compare the results with the Installation/Vessel Limitation
List (IVLL) for the installations concerned (sub-sections 8.6.1 and 9.1.2).
b) Implement the optimised HQR predictors (see recommendation 2 above) in the Helicopter Operations Monitoring Programme (HOMP) analysis, apply the analysis to the HOMP data archive and compare the resulting turbulence mapped around offshore installations with turbulent sectors as derived in a) above (subsections 8.6.2 and 9.1.2).
c) Use the analysis performed in b) above to identify specific severe turbulence events in the HOMP data archive, establish the turbulence levels likely to have been experienced from the associated wind conditions and wind tunnel data for the platforms concerned, and correlate this with the workload values obtained from the HOMP analysis (sub-sections 8.6.2 and 9.1.2).
4 Investigate the operational experience regarding the perceived increase in workload due to degraded visual conditions, and consider conducting further simulator trials to capture equivalent flight in turbulence data at night and in degraded meteorological conditions (sub-sections 4.6.7 and 9.1.2).
5 In the longer term, use data collected from the full-scale implementation of HOMP and optimised HQR predictors (see recommendation 2 above) to routinely map HQR around offshore installations, and make this information available to BHAB Helidecks to help improve and maintain the quality of the IVLL (sub-section 4.6.11).
6 Use data collected from the full-scale implementation of HOMP and optimised HQR predictors (see recommendation 2 above) to obtain evidence of any variation of turbulence induced pilot workload in different helicopter types. If it is apparent that significant differences are experienced across the offshore helicopter types in the fleet, consider extending the desktop simulation study to encompass selected types identified as particularly good or bad in this context (sub-section 5.2).
7 Consider re-assessing the 0.9 m/s vertical wind speed component criterion in the light of the new turbulence criterion (as proposed by [1]). However, note that this will require an improvement to the level of fidelity of the SyCoS model by implementing recent enhancements to produce more authentic control responses and consequently the ability to recognise and respect torque and power limits.
It's a big file (8.6mb). Dial-up users may wish to 'right-click' the link and select 'save target as...' to save the file.
Click: CAA Paper 2004/03
Last edited by Flying Lawyer; 22nd Sep 2004 at 17:20.
A Shorter Version
Stephen Rowe, the managing director of BMT Fluid Mechanics presented a paper based on this work at last weeks European Rotorcraft Forum in Marseille. This is a much smaller piece of bedtime reading - approx 15 pages.
PM me if anyone wants a copy in pdf format.
CRAN
PM me if anyone wants a copy in pdf format.
CRAN
HELIDECK AVAILABLE!!!!! What a load of B******S
What on earth will the CAA think of wasting our money on next? The main comments I hear from around the crewroom is that there has never been any confusion in this regard betwen deck crews and aircraft crews, so why fix something that does not appear to be broken in the first place??!!!!!!!!
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I'd be concerned if I were a UK operator going to helidecks about this. (all of my following comments are based on not having read the document, so take them with a large grain of salt)
While it is useful in an academic sense, what possible use is it going to be in an operational sense?
How are we going to measure turbulence and then quantify it? If we can quantify it, can we then predict it in a manner that would be useful to the operator - it's a bit too late to have the turbulence reported to the pilot on short final where the decision might be 'Do I continue with the prospect that if anything happens I could be blamed for continuing in the knowledge of the turbulence level when my considerable experience tells me that this is OK?'
While it is useful in an academic sense, what possible use is it going to be in an operational sense?
How are we going to measure turbulence and then quantify it? If we can quantify it, can we then predict it in a manner that would be useful to the operator - it's a bit too late to have the turbulence reported to the pilot on short final where the decision might be 'Do I continue with the prospect that if anything happens I could be blamed for continuing in the knowledge of the turbulence level when my considerable experience tells me that this is OK?'
I think the aim is to be able to derive scientifically derived, as opposed to emperical, limitations on Ops, when turbulence is predicted to reach certain levels. At present the limits in the HLL are best guestimates based on experience but do not have any basis in fact.
In a similar vein, the whole concept of pitch, roll and heave limits is being re-evaluated to come up with something based on facts and not incorrect assumptions.
In a similar vein, the whole concept of pitch, roll and heave limits is being re-evaluated to come up with something based on facts and not incorrect assumptions.
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Three comments:
1) What has happened that marks this need? remember the thread on "hard Cat A" where the prayer I have is that we first fix what is broken, then move to the fun and pleasure of fixing what is not.
2) What would we do with the data? Who knows what a helicopter can stand in upgust and side gust at low speed? What new tests will be cooked up, and will they bear any resemblence to the operating environment being questioned?
3) Will the regulators in their zest to make a new, shinier rule, make all helicopters the same by simply using the lowest common denominator when they set the rule? Will they ignore the very high pitch, roll and yaw control power of some machines, and restrict operations for all based on the assumed properties of the poorest helos?
1) What has happened that marks this need? remember the thread on "hard Cat A" where the prayer I have is that we first fix what is broken, then move to the fun and pleasure of fixing what is not.
2) What would we do with the data? Who knows what a helicopter can stand in upgust and side gust at low speed? What new tests will be cooked up, and will they bear any resemblence to the operating environment being questioned?
3) Will the regulators in their zest to make a new, shinier rule, make all helicopters the same by simply using the lowest common denominator when they set the rule? Will they ignore the very high pitch, roll and yaw control power of some machines, and restrict operations for all based on the assumed properties of the poorest helos?
I don't think anyone is saying that "anything is broken".
Historically, platform/rig designers tended to site helidecks on the structure as an after thought, and were more concerned with the functionality of the 'rig' for its purpose than how the helideck location would be affected by its environment. So, traditionally, the hapless helicopter pilot turned up and dealt with the conditions as best he could. Sometimes they will be benign and landing is a simple task to accomplish, other times it will be downright frightening, and quite likely dangerous leaving the crew sighing a breath of relief when on the deck or possibly having to go around.
So to recognise this fact of life, the operators created restrictions, based on wind sector and strength, for those rigs with known problems (doesn't take too many approaches to the Brae with a 50 kt wind from the NW to realise that it's not big and it's not clever to keep doing it!)
Those limits were based on what 'felt right' for a particular type based on qualatative assessment by experienced pilots, such as the company test pilots, and would take the form of weight penalties that became progressively harsher as wind strength increased and normally reaching a limiting wind speed when ops would be banned.
Do these limits work? Well, up to a point they must do. Are the crew being put under an excessive workload such that they will lack spare capacity to deal with subsequent problems? Who knows; no-one calculated it, but probably in some cases. Are the passengers being exposed to a risk they should not be? Ditto.
With modern computing capabilities and simulation techniques, it would seem entirely sensible to look at this problem more carefully, surely? For any given platform design, a set of restricted crieria could be drawn up which would vary from type to type, based on their individual control and performance characteristics.
In what way can this be construed as a bad thing?
Do we really advocate the phillosophy of "off you go Bloggs to the XYZ rig which has a 60 kt wind, clad derricks and turbine exhaust plumes, and have a go, see how it feels and if you don't like it come back"?
Do we expect our B777 pilot taking us on holiday to 'shoot an approach' in a gusting 40 kt crosswind to see if "he can manage it"? I hope not; we expect him to say "no that's out of limits.
Where's the difference?
As I say, exactly the same principle applies to Pitch, Roll and Heave limits; some sort of limits had to be set originally, but with time it is obvious they are deficient in their logic. 3 degrees of roll for a deck 30 ft ASL is going to generate totally different accelerations and lateral displacements than one that is 130 ft ASL. Therefore an alternative is being sought.
I don't think the terms "zest", "cooked up" or "lowest common denominator" really apply in this context.
Historically, platform/rig designers tended to site helidecks on the structure as an after thought, and were more concerned with the functionality of the 'rig' for its purpose than how the helideck location would be affected by its environment. So, traditionally, the hapless helicopter pilot turned up and dealt with the conditions as best he could. Sometimes they will be benign and landing is a simple task to accomplish, other times it will be downright frightening, and quite likely dangerous leaving the crew sighing a breath of relief when on the deck or possibly having to go around.
So to recognise this fact of life, the operators created restrictions, based on wind sector and strength, for those rigs with known problems (doesn't take too many approaches to the Brae with a 50 kt wind from the NW to realise that it's not big and it's not clever to keep doing it!)
Those limits were based on what 'felt right' for a particular type based on qualatative assessment by experienced pilots, such as the company test pilots, and would take the form of weight penalties that became progressively harsher as wind strength increased and normally reaching a limiting wind speed when ops would be banned.
Do these limits work? Well, up to a point they must do. Are the crew being put under an excessive workload such that they will lack spare capacity to deal with subsequent problems? Who knows; no-one calculated it, but probably in some cases. Are the passengers being exposed to a risk they should not be? Ditto.
With modern computing capabilities and simulation techniques, it would seem entirely sensible to look at this problem more carefully, surely? For any given platform design, a set of restricted crieria could be drawn up which would vary from type to type, based on their individual control and performance characteristics.
In what way can this be construed as a bad thing?
Do we really advocate the phillosophy of "off you go Bloggs to the XYZ rig which has a 60 kt wind, clad derricks and turbine exhaust plumes, and have a go, see how it feels and if you don't like it come back"?
Do we expect our B777 pilot taking us on holiday to 'shoot an approach' in a gusting 40 kt crosswind to see if "he can manage it"? I hope not; we expect him to say "no that's out of limits.
Where's the difference?
As I say, exactly the same principle applies to Pitch, Roll and Heave limits; some sort of limits had to be set originally, but with time it is obvious they are deficient in their logic. 3 degrees of roll for a deck 30 ft ASL is going to generate totally different accelerations and lateral displacements than one that is 130 ft ASL. Therefore an alternative is being sought.
I don't think the terms "zest", "cooked up" or "lowest common denominator" really apply in this context.
A couple of things that I would add to 212man's defense of this research and graphic description of flying to rigs in turbulent conditions:
This, my friends, is progress and not to be scoffed at.
- This research was undertaken as a result of an accident to an S61 in conditions under which it should not have occurred;
- the first target of the research is the rig design process;
- the wind tunnel data that is produced when the rig is designed and tested has never been used to provide data for an initial HLL (IVLL);
- the HOMP system contains the weather data (produced from another system and inverted into the data set), the control movements, and the ability to analyse the pilot workload. At the moment pilot workload is assessed using a local algorithm produced by the (very able) HOMP manager. In the near future it will be replaced by a more specific algorithm that has been produced using Cooper Harper ratings.
This, my friends, is progress and not to be scoffed at.
Last edited by JimL; 27th Sep 2004 at 15:28.
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Don't get me wrong - I'm all for having better data to make decisions with. But the data has to be good, relevant data. My concern is that any data taken will not be as complete as it should be, that it may eventuallly be interpretted incorrectly, and we'll end up with restrictions and limitations that will negatively impact the industry.
Is this data taking going to include comprehensive information on the wind, gusts, vertical and lateral turbulence, aircraft motion, AFCS actuator operation, visual cues, and so on? Who is going to interpret it?
I know of an accident on a rooftop helipad where the helicopter should not have been operating in very gusty winds. There did not appear to be any consideration of the operating environment when the helipad was 'approved'. The question of the competence (read training and understanding of what was being approved) of the approver was never answered that I know of, nor whether winds or turbulence were ever addressed.
Ship operating limitations would be a good place to start looking at this (the problem obviously is that it's hard to drive an oil rig to generate the necessary wind envelopes...)
Is this data taking going to include comprehensive information on the wind, gusts, vertical and lateral turbulence, aircraft motion, AFCS actuator operation, visual cues, and so on? Who is going to interpret it?
I know of an accident on a rooftop helipad where the helicopter should not have been operating in very gusty winds. There did not appear to be any consideration of the operating environment when the helipad was 'approved'. The question of the competence (read training and understanding of what was being approved) of the approver was never answered that I know of, nor whether winds or turbulence were ever addressed.
Ship operating limitations would be a good place to start looking at this (the problem obviously is that it's hard to drive an oil rig to generate the necessary wind envelopes...)
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Like NickLappos, I too have a prayer and that is that folk would read reports properly before passing comment.
As JimL has already helpfully pointed out, the turbulence criterion is for use during the initial rig design or modification process (along with the other criteria contained in CAP 437) and should help to create rigs that are more helicopter friendly and improve the information that goes into the HLL.
The control movement based pilot workload algorithms are being implemented in HOMP primarily to validate the maximum turbulence level produced by the research prior to inclusion in CAP 437. A secondary benefit will be to susequently use HOMP to establish polar plots a bit like SHOLs (workload level as a function of wind speed and direction - see Figures 7.4 and 7.6 in CAA Paper 2002/02 which are based on an 'informal' turbulence algorithm) for all rigs, and also permit continuous monitoring for unannounced changes to topsides (e.g. cladding of derriks, use of air gap for storage). This will support the existing turbulence report form process by automatically (via the HOMP ground station) providing consistent and objective data on the wind environment around all rigs.
As JimL has already helpfully pointed out, the turbulence criterion is for use during the initial rig design or modification process (along with the other criteria contained in CAP 437) and should help to create rigs that are more helicopter friendly and improve the information that goes into the HLL.
The control movement based pilot workload algorithms are being implemented in HOMP primarily to validate the maximum turbulence level produced by the research prior to inclusion in CAP 437. A secondary benefit will be to susequently use HOMP to establish polar plots a bit like SHOLs (workload level as a function of wind speed and direction - see Figures 7.4 and 7.6 in CAA Paper 2002/02 which are based on an 'informal' turbulence algorithm) for all rigs, and also permit continuous monitoring for unannounced changes to topsides (e.g. cladding of derriks, use of air gap for storage). This will support the existing turbulence report form process by automatically (via the HOMP ground station) providing consistent and objective data on the wind environment around all rigs.
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What?!
Any chance of starting a Test Pilot / thinks he's a Test Pilot page.
At least then you can wow each other with ever more ludicrous acronyms without boring the c**p out of those of us who commit that most heinous of crimes, "pitching up, deciding we don't like it and going home again"
At least then you can wow each other with ever more ludicrous acronyms without boring the c**p out of those of us who commit that most heinous of crimes, "pitching up, deciding we don't like it and going home again"
Howcanwebeexpectedtoflylikeeagles
whensurroundedbyturkeys
Turbulence on offshore platforms has been a subject which has been doing the rounds since I was very wet behind the ears (and I am still drying out). Over the years we, on the UK sector of the North Sea, have produced a set of operational procedures and limitations which are used by all three operators called the Helideck Limitations List (HLL).
Turbulence by its very nature is chaotic and I don't believe we will be able to come up with a significantly better solution. Most newer helidecks have much less turbulence than the first generations ones which had no thought put into this problem. Modern ones usually have the helidecks on the west or south west corner so that the prevailing wind gives a clean airflow. Slab effect has also been reduced by providing large spaces between the helideck and the structures below it. No platform will be turbulence free in all wind conditions.
There are two issues from a practical point of view.
The first is to ensure the pilot is not put into a dangerous situation from which he/she will have a poor chance of recovering. At best, this might result in an overtorque or heavy landing which may require some sort of engineering inspection. The worst may include an inadvertent contact of inappropriate parts of the helicopter and the offshore installation resulting in a catastrophic event.
The second requirement is maintaining a standard of operational consistency to ensure we are all singing from the same hymn sheet. The customer and the pilots have some comfort in having a set of operational limitations which, by no means being scientifically derived, are the result of operational experience which usually errs on the safe side. This means we have the ability to predict the likelyhood of the job getting done or being postponed without having to think about whether pilot A or B is braver or better than pilot C or D. This helps eliminate commercial or peer pressure to get the job done when common sense should say "let's wait for a better time".
It is usually fairly obvious when turbulence is likely to exist by looking for the likely sources. A helideck in the lee of large exhaust pipes and/or obstructions should always be treated cautiously even in light wind conditions. Many of us are taught to fly an approach which is designed primarily to minimise the risk in the event of an engine malfunction i.e, keep translational lift as long as possible which will create a low power approach with a highish rate of descent. In the event of turbulence, this will usually require large power inputs to arrest the helicopter's inertia as it approaches the deck. I would suggest that the chance of engine malfunction during approach is very remote. If turbulence is likely, you are going to be in a much better position if your final approach to the deck is made at a slow forward speed and a slow rate of descent. This means having power applied early so that there is no need for large changes of power close to the hard objects.
It is also a good idea to brief your passengers before the approach that it is likely to be bumpy. This usually causes all turbulence to disappear and the passengers left wondering what the heck you were talking about. But I would rather have that than having to fill in all the paperwork following a heavy landing or overtorque.
Turbulence by its very nature is chaotic and I don't believe we will be able to come up with a significantly better solution. Most newer helidecks have much less turbulence than the first generations ones which had no thought put into this problem. Modern ones usually have the helidecks on the west or south west corner so that the prevailing wind gives a clean airflow. Slab effect has also been reduced by providing large spaces between the helideck and the structures below it. No platform will be turbulence free in all wind conditions.
There are two issues from a practical point of view.
The first is to ensure the pilot is not put into a dangerous situation from which he/she will have a poor chance of recovering. At best, this might result in an overtorque or heavy landing which may require some sort of engineering inspection. The worst may include an inadvertent contact of inappropriate parts of the helicopter and the offshore installation resulting in a catastrophic event.
The second requirement is maintaining a standard of operational consistency to ensure we are all singing from the same hymn sheet. The customer and the pilots have some comfort in having a set of operational limitations which, by no means being scientifically derived, are the result of operational experience which usually errs on the safe side. This means we have the ability to predict the likelyhood of the job getting done or being postponed without having to think about whether pilot A or B is braver or better than pilot C or D. This helps eliminate commercial or peer pressure to get the job done when common sense should say "let's wait for a better time".
It is usually fairly obvious when turbulence is likely to exist by looking for the likely sources. A helideck in the lee of large exhaust pipes and/or obstructions should always be treated cautiously even in light wind conditions. Many of us are taught to fly an approach which is designed primarily to minimise the risk in the event of an engine malfunction i.e, keep translational lift as long as possible which will create a low power approach with a highish rate of descent. In the event of turbulence, this will usually require large power inputs to arrest the helicopter's inertia as it approaches the deck. I would suggest that the chance of engine malfunction during approach is very remote. If turbulence is likely, you are going to be in a much better position if your final approach to the deck is made at a slow forward speed and a slow rate of descent. This means having power applied early so that there is no need for large changes of power close to the hard objects.
It is also a good idea to brief your passengers before the approach that it is likely to be bumpy. This usually causes all turbulence to disappear and the passengers left wondering what the heck you were talking about. But I would rather have that than having to fill in all the paperwork following a heavy landing or overtorque.
Last edited by HughMartin; 9th Oct 2004 at 05:06.
UK offshore - "deck available"
What do the offshore pilots think of the new terminology of "Deck availabe for landing" replacing "Deck is clear for landing".
My thoughts are it is replacing a clear concise reply with waffle. By all means change the previous "negative deck clear" with "deck unavailable" to avoid confusion.
I must admit in 15+yrs on the N Sea I have never heard "negative deck clear" it has always been "standby" while the deck crew assembled or no reply because nobody had told the deck crew your ETA!!!
This is a change to address a perceived problem that doesn,t exist
HF
My thoughts are it is replacing a clear concise reply with waffle. By all means change the previous "negative deck clear" with "deck unavailable" to avoid confusion.
I must admit in 15+yrs on the N Sea I have never heard "negative deck clear" it has always been "standby" while the deck crew assembled or no reply because nobody had told the deck crew your ETA!!!
This is a change to address a perceived problem that doesn,t exist
HF
What about " Green helideck " or " Red helideck " ?
The HLO, not beeing a qualified ATC controller is in principle not authorized to give a proper landing clearance.
The HLO, not beeing a qualified ATC controller is in principle not authorized to give a proper landing clearance.